Arduino Forum

This is my first post on here so please be patient if I miss any etiquettes. :)

I am currently in the process of making a quadcopter with an Arduino Uno as the flight controller. I have a 3S, 3 cell 11.1v LiPo battery powering my ESC's and Arduino.

The ESC: Racerstar RS20Ax4 20A 4 in 1 Blheli_S Opto

The Motors: BR2205 2300V Brushless motors.

My problem occurs when I force my motors to 80% power (Limited from 100% to save their lives) in less than a second. This causes a transient that has ended up frying the Arduino Uno which is controlling the receiver, ESC's, ect. Luckily everything else was undamaged. I replaced the Arduino and everything was good again.

Under all other conditions I have tested so far, everything works fine, and the arduino ticks over normally. :)

My question; How do I go about modeling an Arduino Uno as a load to see how the current and voltage affect the Arduino Uno when it is subjected to this condition.

I have the arduino in parallel with the ESC's powered by the LiPo. This is because the Arduino can comfortably operate with 11.1V and ESC's at 11.1V. (I am using the 9V plug thingy to power the Arduino)

The below is an LTSpice model I have made to model the ESC's, but I am having problems on modeling the Arduino.

Has anyone done this? Does any one know how I could go about this?

Ps. I have looked and found that UBEC's can arrest this problem, but I like modeling everything myself :)

You don't need to model, you add protection circuitry to prevent it happening. With hard motor brakingyou are pushing current back into the battery which is causing a voltage spike - normally a LiPopack should absorb that easily, so something else is happening I think - bad wiring or something,leading to the supply rail jumping a lot. Perhaps the LiPo over-charge prevention circuit is tripping?

To prevent the supply rail jumping too high, a clamp circuit is needed to limit the voltage and dissipatethe energy harmlessly.

See this page and search for "with transistor buffer": https://www.electronics-notes.com/articles/analogue_circuits/power-supply-electronics/over-voltage-protection.php (https://www.electronics-notes.com/articles/analogue_circuits/power-supply-electronics/over-voltage-protection.php)

The transistor should be a power transistor able to absorb some energy without immediately frying, soTO220 package or similar.

Under the right circumstances, you can operate an UNO at 11.1V. However as soon as there are inductive loads like motors in the circuit, you can't rely on that 11.1V staying within the limits of the Arduino.

Get another voltage regulator between the battery and the UNO. You should find that it's not hard to find them with input ratings up to 36V. Go direct to 5V, bypassing the Arduino's regulator. Follow the regulator's recommendations for input and output capacitors.

For fun, take one of your brushless motors that's not connected to anything and try to spin the shaft. It should be easy to spin. Now grab all the wires coming out of the motor and twist the bare ends together. Try to spin it again. It is surprising how much difference this makes. Now imagine the rotor spinning at a few thousand RPM and think about how much energy is stored in that rotational inertia, coming back down the wires to your Arduino.

TomGeorge, I am using a 4in1 ESC so na it is not in a Star Configuration. And No, its on the same power leads as the ESC with no protection circuitry.

When this happened, the smell of smoke came from the Arduino. Im pretty sure there was a voltage spike through the arduino and just killed it.

MoragnS Yes I agree, but this will not occur when there are no sharp changed in the power drawn from the motors. right? Im an Electrical Engineer with one year to go till I graduate, so I beleive I have a half decent idea whats happening.

The battery is the source of power. The wires between the battery and other things have inductance and resistance. And no, the motors aren't drawing constant power - they can even be feeding power back to the battery. So the battery is the most stable element of the system. Delicate electronics should have their own wire from the battery.

If you don't tell us the details of the "4in1" or any other components, then we can't help.